Novel approaches to reduce the risk of age-related cognitive decline and Alzheimer's disease and related dementias (ADRD) in older adults are urgently needed given the aging of the population. Epidemiologic studies demonstrate that peripheral hearing loss in older adults is strongly and independently associated with accelerated cognitive decline and incident dementia. Hypothesized mechanistic pathways underlying this observed association include the effects of poor hearing and distorted peripheral encoding of sound on cognitive load, brain structure/function, and/or reduced social engagement. Importantly, these pathways may be modifiable with comprehensive hearing loss treatment consisting of the use of hearing technologies (hearing aids, other integrated hearing assistive devices) and rehabilitative training. The ACHIEVE trial will recruit 70-84 year-old cognitively-normal older adults with hearing loss who will be randomized 1:1 to the hearing intervention (hearing needs assessment, fitting of hearing devices, education/counseling) or control intervention (individualized successful aging education sessions with a health educator covering healthy aging topics). This trial will have 90% power to detect a net effect size of 0.26 for the difference in cognitive change between the hearing intervention vs successful aging intervention at 3 years follow-up (corresponding to a 35% slowing in the annual rate of cognitive decline). The ACHIEVE trial has the following aims: Aim 1 To determine ?? the effect of hearing rehabilitative intervention versus a successful aging control intervention on rates of cognitive decline (primary outcome measure) in 70 84 year old cognitively-normal older adults with hearing loss. Aim 2 To determine the effect of hearing rehabilitative intervention versus a successful aging control intervention on secondary outcome measures of adjudicated incident dementia, physical and social functioning, health-related quality of life, and physical activity. The ACHIEVE trial began recruitment in January 2018 and reached the target N of 850 on July 17, 2019. This application for an administrative supplement to the ACHIEVE randomized trial is to support an increase in the sample size of the ACHIEVE study from the original target of N = 850 up to potentially N ~ 1000. An extension in recruitment is consistent with recent discussions from the ACHIEVE DSMB which convened on June 27, 2019 and ?supports consideration of a modest extension of the planned enrollment period to provide additional robustness of the study design to possible violations in the assumptions used in the power calculations?.